The invention relates to effective and environmentally compatible compositions that prevent terrestrial molluscs from feeding on plant tissue.
Terrestrial pulmonate gastropod molluscs, slugs and snails (collectively, "molluscs") are significant crop pests that affect commercial agriculture and horticulture, and domestic gardening. Control of these pests can be achieved through physical trapping, hand picking, physical or chemical barriers, or with chemical controls. Poison baits such as metaldehyde or methiocarb are synthetic chemicals that are effective in poisoning slugs, but snails have developed resistance to some of these pesticides. An additional disadvantage of using such synthetic pesticides is the potential hazard to children and pets should they consume or contact the poison baits.
Certain aquatic molluscs, including snails of the genera Biomphalaria, Bulinus and Oncomelania, have been implicated in the transmission of schistosomiasis, a parasitic disease endemic throughout South America, Africa, and the Far East. These molluscs that live in stagnant or slow moving water serve as vectors for the schistosomes that cause human infection. Schistosomiasis and the organisms responsible for the disease have attracted the attention of many researchers since over 200 million people are affected by the disease.
Although various anti-schistosomal drugs are known, researchers have also sought means to destroy the aquatic mollusc vector. Accordingly, certain naturally occurring compounds have been widely studied and identified as being compounds effective to kill the aquatic molluscs when added to the aquatic environment in which the molluscs live. Among such effective compounds are triterpenoid saponins and spirostanol saponins. These compounds can be extracted from many plants native to the areas affected by schistosomiasis. These plants include the desert palm (Balanites aegyptiaca), the sisal plant (Agave sisalana), and the cashew tree (Anacardium occidentale.L).
Despite the great deal of attention directed to the control of aquatic molluscs using saponin-containing materials, no investigation is known to previously have been made to use these compounds to control terrestrial molluscs. This is so despite the significant problems posed by terrestrial molluscs as crop pests.
Sapogenins are present in several monocot families (e.g., Liliaceae, Amarylidaceae, and Dioscoreaceae) and in dicots (e.g., Scrophulariaceae and Solanoceae). In plants, the sapogenins are combined with sugars to form saponins. The sapogenin may be a steroid or a triterpene, and the sugar moiety may be glucose, galactose, a pentose or a methyl pentose.
Saponins also are widely used in the beverage industry as a foaming agent. In addition, plant extracts containing saponins have been used to enhance microbial growth in septic fields, for reducing ammonia and hydrogen sulfide odors and sludge accumulation in manure holding ponds and lagoons, to control ammonia emissions in floor-raised poultry, and in a variety of other uses. Steroid saponins are also known to be effective in improving crop yields when growing conditions are less than ideal, usually due to drought conditions. The addition of steroid saponins to irrigation water serves to substantially increase crop yields while lowering water demands. In addition, steroid saponins show promise as animal feed additives where they apparently optimize the conditions for microorganisms living in the digestive tract of the animal.
The efficient and safe control of terrestrial molluscs would be of great benefit to agriculture and horticulture. Currently used non-chemical control means are not entirely effective, and quite often can be tedious to use. Currently used chemical control means for terrestrial molluscs rely upon the use of synthetic chemicals that can pose significant dangers to humans, pets, and to the environment. Accordingly, there is a need for a safe, chemically based means that prevent and control the infestation of living plants by terrestrial molluscs.
Thus, it is an object of the invention to provide a method for preventing terrestrial molluscs from feeding upon living plants. A further object of the invention is to provide a safe and effective composition, composed of natural, biodegradable active ingredients, which may be applied to living plants to serve as a terrestrial mollusc antifeedant. Another object of the invention is to provide a safe, effective and biodegradable composition that is fatally toxic to terrestrial molluscs. Other objects of the invention will be apparent upon reading the following disclosure.